Oil recovery rates to improve

By Ibrahim Kasita

A debate on the optimal percentage of crude oil that should be extracted from the ground has started underscoring the need for dialogue and consultations with stakeholders in public policy making process for the prudent management of Uganda’s petroleum resources.

The energy ministry and mineral development revealed last week that 31% of the 635 million barrels of crude oil in place in the Kingfisher Field will be recovered. It means that only 196 million barrel will be extracted during the lifespan of the field.

Prior to the disclosure, the energy and mineral development minister, Irene Muloni, said Uganda has so-far proven reserves in place of  3.5 billion barrels and large areas of finding petroleum resources is yet to be explored. But she added that only 1.2 billion barrels of recoverable oil and gas have been confirmed.

This means that Uganda’s recovery rate policy of the entire petroleum resources in the Lake Albert basin is the average 34.28%.

The recovery rate or sometimes referred to recovery factor is a dynamic value, representing the estimated percentage of the total oil in  place volume that can be recovered.

However, a debate on the best extraction rates Uganda should pursue to efficiently produce the country’s oil and gas resources as per objective three of the National Oil and Gas Policy 2008 has started.

Majority believe that the average extraction rate of 34.28% is “too low” and there is a need to mandate the oil companies to recover at least 60% for prudent management of the petroleum reserves not only for the current generation but also the future.

However, the level of oil recovery is dependent on numerous parameters, such as rock and fluid properties, reservoir drive mechanism and production technology, variations in the formation and the development process.

Oil recovery rates can vary from 10% to more than 80% depending on reservoir properties and recovery methods. Studies estimate that global average recovery factor to be 29% which is expected to improve to 38% with new technologies.

The petroleum exploration and production department of the energy ministry says some of the fields have “stacked reservoirs” and therefore each reservoir unit in the field may have a different recoverable rate.

“From the Field Development Plans and Petroleum Reservoir Reports that are under discussion, recoverable rates for the different reservoirs in the different fields average at about 30% under primary depletion,” the ministry said in response to New Vision questions.

Recovery methods

The ministry said information is never conclusive at the field development plan stage until when production commences
and more data is acquired that may be used to improve the recovery factors.

“Therefore whereas there is an estimate at the point of field development plans and Petroleum Reservoir Report submission, these recoverable rates are not static and can and do change over the life cycle of the field, especially as a result of improved understanding of the field and improvement in technology.”

There are three methods of oil recovery; the primary, secondary and tertiary recovery methods.

● Primary recovery method is the production without pressure and chemical support, with an increment of 5-10% if enhanced oil recovery methods are deployed in the fields.

● Secondary recovery methods utilise injection of water and/or gas to maintain pressure, thus feeding additional energy to the reservoir. About 30-50% of the oil in place can be recovered by use of primary and secondary recovery methods.

● Tertiary recovery methods, or enhanced oil recovery (EOR), include more complex methods, such as injection of polymer solutions, surfactants, microbes, nitrogen or carbon dioxide, capable of influencing rock and fluid properties.